This book, written by Martin Koch, shows how to build two different styles of solid body lap steels illustrated with 225 photos and 40 line drawings. Full review coming.
Find out more about this book on lap steel guitar building.
Next, a real easy way to put your steel together in our opinion is using a kit, such as that offered by a company formerly known as Dynalap. If you find a Dynalap, pick it up quick, they're hard to find, affordable, and are great guitars for practice or regular gigging.

For the low price of $275, you get everything you need to put your guitar together.

The only drawback is that you don't get a true custom creation. However, the Dynalap in our opinion looks and sounds like a real guitar!
Finally, when you're looking for parts and tools, especially the little things like output jacks and pots, we've always gone to Stew Mac.

If you're never heard of them before, get ready to be in guitar parts heaven.